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/spec/6 Draft specs 6/PAYLOADS

6/PAYLOADS

Version: 0.4

Status: Draft

Authors: Adam Babik adam@status.im, Andrea Maria Piana andreap@status.im, Oskar Thorén oskar@status.im (alphabetical order)

Abstract

This specification describes how the payload of each message in Status looks like. It is primarily centered around chat and chat-related use cases.

The payloads aims to be flexible enough to support messaging but also cases described in the Status Whitepaper as well as various clients created using different technologies.

Table of Contents

Introduction

This document describes the payload format and some special considerations.

Payload wrapper

The node wraps all payloads in a protobuf record record:

message StatusProtocolMessage {
  bytes signature = 4001;
  bytes payload = 4002;
}

signature is the bytes of the signed SHA3-256 of the payload, signed with the key of the author of the message. The node needs the signature to validate authorship of the message, so that the message can be relayed to third parties. If a signature is not present, but an author is provided by a layer below, the message is not to be relayed to third parties, and it is considered plausibly deniable.

Encoding

The node encodes the payload using Protobuf

Types of messages

Message

The type ChatMessage represents a chat message exchanged between clients.

Payload

The protobuf description is:

message ChatMessage {
  // Lamport timestamp of the chat message
  uint64 clock = 1;
  // Unix timestamps in milliseconds, currently not used as we use Whisper/Waku as more reliable, but here
  // so that we don't rely on it
  uint64 timestamp = 2;
  // Text of the message
  string text = 3;
  // Id of the message that we are replying to
  string response_to = 4;
  // Ens name of the sender
  string ens_name = 5;
  // Chat id, this field is symmetric for public-chats and private group chats,
  // but asymmetric in case of one-to-ones, as the sender will use the chat-id
  // of the received, while the receiver will use the chat-id of the sender.
  string chat_id = 6;

  // The type of message (public/one-to-one/private-group-chat)
  MessageType message_type = 7;
  // The type of the content of the message
  ContentType content_type = 8;

  oneof payload {
    StickerMessage sticker = 9;
    ImageMessage image = 10;
    AudioMessage audio = 11;
  }

  enum MessageType {
    UNKNOWN_MESSAGE_TYPE = 0;
    ONE_TO_ONE = 1;
    PUBLIC_GROUP = 2;
    PRIVATE_GROUP = 3;
    // Only local
    SYSTEM_MESSAGE_PRIVATE_GROUP = 4;}
  enum ContentType {
    UNKNOWN_CONTENT_TYPE = 0;
    TEXT_PLAIN = 1;
    STICKER = 2;
    STATUS = 3;
    EMOJI = 4;
    TRANSACTION_COMMAND = 5;
    // Only local
    SYSTEM_MESSAGE_CONTENT_PRIVATE_GROUP = 6;
    IMAGE = 7;
    AUDIO = 8;
  }
}

Payload

Field Name Type Description
1 clock uint64 The clock of the chat
2 timestamp uint64 The sender timestamp at message creation
3 text string The content of the message
4 response_to string The ID of the message replied to
5 ens_name string The ENS name of the user sending the message
6 chat_id string The local ID of the chat the message is sent to
7 message_type MessageType The type of message, different for one-to-one, public or group chats
8 content_type ContentType The type of the content of the message
9 payload `Sticker Image

Content types

A node requires content types for a proper interpretation of incoming messages. Not each message is plain text but may carry different information.

The following content types MUST be supported:

  • TEXT_PLAIN identifies a message which content is a plaintext.

There are other content types that MAY be implemented by the client:

  • STICKER
  • STATUS
  • EMOJI
  • TRANSACTION_COMMAND
  • IMAGE
  • AUDIO
Mentions

A mention MUST be represented as a string with the @0xpk format, where pk is the public key of the user account to be mentioned, within the text field of a message with content_type TEXT_PLAIN. A message MAY contain more than one mention. This specification RECOMMENDs that the application does not require the user to enter the entire pk. This specification RECOMMENDs that the application allows the user to create a mention by typing @ followed by the related ENS or 3-word pseudonym. This specification RECOMMENDs that the application provides the user auto-completion functionality to create a mention. For better user experience, the client SHOULD display a known ens name or the 3-word pseudonym corresponding to the key instead of the pk.

Sticker content type

A ChatMessage with STICKER Content/Type MUST also specify the ID of the Pack and the Hash of the pack, in the Sticker field of ChatMessage

message StickerMessage {
  string hash = 1;
  int32 pack = 2;
}
Image content type

A ChatMessage with IMAGE Content/Type MUST also specify the payload of the image and the type.

Clients MUST sanitize the payload before accessing its content, in particular:

  • Clients MUST choose a secure decoder
  • Clients SHOULD strip metadata if present without parsing/decoding it
  • Clients SHOULD NOT add metadata/exif when sending an image file for privacy and security reasons
  • Clients MUST make sure that the transport layer constraints the size of the payload to limit they are able to handle securely
message ImageMessage {
  bytes payload = 1;
  ImageType type = 2;
  enum ImageType {
    UNKNOWN_IMAGE_TYPE = 0;
    PNG = 1;
    JPEG = 2;
    WEBP = 3;
    GIF = 4;
  }
}
Audio content type

A ChatMessage with AUDIO Content/Type MUST also specify the payload of the audio, the type and the duration in milliseconds (duration_ms).

Clients MUST sanitize the payload before accessing its content, in particular:

  • Clients MUST choose a secure decoder
  • Clients SHOULD strip metadata if present without parsing/decoding it
  • Clients SHOULD NOT add metadata/exif when sending an audio file for privacy and security reasons
  • Clients MUST make sure that the transport layer constraints the size of the payload to limit they are able to handle securely
message AudioMessage {
  bytes payload = 1;
  AudioType type = 2;
  uint64 duration_ms = 3;
  enum AudioType {
    UNKNOWN_AUDIO_TYPE = 0;
    AAC = 1;
    AMR = 2;
  }
}

Message types

A node requires message types to decide how to encrypt a particular message and what metadata needs to be attached when passing a message to the transport layer. For more on this, see 3/WHISPER-USAGE and 10/WAKU-USAGE.

The following messages types MUST be supported:

  • ONE_TO_ONE is a message to the public group
  • PUBLIC_GROUP is a private message
  • PRIVATE_GROUP is a message to the private group.

Clock vs Timestamp and message ordering

If a user sends a new message before the messages sent while the user was offline are received, the new message is supposed to be displayed last in a chat. This is where the basic algorithm of Lamport timestamp would fall short as it's only meant to order causally related events.

The status client therefore makes a "bid", speculating that it will beat the current chat-timestamp, s.t. the status client's Lamport timestamp format is: clock = max({timestamp}, chat_clock + 1)`

This will satisfy the Lamport requirement, namely: a -> b then T(a) < T(b)

timestamp MUST be Unix time calculated, when the node creates the message, in milliseconds. This field SHOULD not be relied upon for message ordering.

clock SHOULD be calculated using the algorithm of Lamport timestamps. When there are messages available in a chat, the node calculates clock's value based on the last received message in a particular chat: max(timeNowInMs, last-message-clock-value + 1). If there are no messages, clock is initialized with timestamp's value.

Messages with a clock greater than 120 seconds over the Whisper/Waku timestamp SHOULD be discarded, in order to avoid malicious users to increase the clock of a chat arbitrarily.

Messages with a clock less than 120 seconds under the Whisper/Waku timestamp might indicate an attempt to insert messages in the chat history which is not distinguishable from a datasync layer re-transit event. A client MAY mark this messages with a warning to the user, or discard them.

The node uses clock value for the message ordering. The algorithm used, and the distributed nature of the system produces casual ordering, which might produce counter-intuitive results in some edge cases. For example, when a user joins a public chat and sends a message before receiving the exist messages, their message clock value might be lower and the message will end up in the past when the historical messages are fetched.

Chats

Chat is a structure that helps organize messages. It's usually desired to display messages only from a single recipient, or a group of recipients at a time and chats help to achieve that.

All incoming messages can be matched against a chat. The below table describes how to calculate a chat ID for each message type.

Message Type Chat ID Calculation Direction Comment
PUBLIC_GROUP chat ID is equal to a public channel name; it should equal chatId from the message Incoming/Outgoing
ONE_TO_ONE let P be a public key of the recipient; hex-encode(P) is a chat ID; use it as chatId value in the message Outgoing
user-message let P be a public key of message's signature; hex-encode(P) is a chat ID; discard chat-id from message Incoming if there is no matched chat, it might be the first message from public key P; the node MAY discard the message or MAY create a new chat; Status official clients create a new chat
PRIVATE_GROUP use chatId from the message Incoming/Outgoing find an existing chat by chatId; if none is found, the user is not a member of that chat or the user hasn't joined that chat, the message MUST be discarded

Contact Update

ContactUpdate is a message exchange to notify peers that either the user has been added as a contact, or that information about the sending user have changed.

message ContactUpdate {
  uint64 clock = 1;
  string ens_name = 2;
  string profile_image = 3;
}

Payload

Field Name Type Description
1 clock uint64 The clock of the chat with the user
2 ens_name string The ENS name if set
3 profile_image string The base64 encoded profile picture of the user

Contact update

A client SHOULD send a ContactUpdate to all the contacts each time:

  • The ens_name has changed
  • A user edits the profile image

A client SHOULD also periodically send a ContactUpdate to all the contacts, the interval is up to the client, the Status official client sends these updates every 48 hours.

SyncInstallationContact

The node uses SyncInstallationContact messages to synchronize in a best-effort the contacts to other devices.

message SyncInstallationContact {
  uint64 clock = 1;
  string id = 2;
  string profile_image = 3;
  string ens_name = 4;
  uint64 last_updated = 5;
  repeated string system_tags = 6;
}

Payload

Field Name Type Description
1 clock uint64 clock value of the chat
2 id string id of the contact synced
3 profile_image string base64 encoded profile picture of the user
4 ens_name string ENS name of the contact
5 array[string] Array of system_tags for the user, this can currently be: ":contact/added", ":contact/blocked", ":contact/request-received"

SyncInstallationPublicChat

The node uses SyncInstallationPublicChat message to synchronize in a best-effort the public chats to other devices.

message SyncInstallationPublicChat {
  uint64 clock = 1;
  string id = 2;
}

Payload

Field Name Type Description
1 clock uint64 clock value of the chat
2 id string id of the chat synced

PairInstallation

The node uses PairInstallation messages to propagate information about a device to its paired devices.

message PairInstallation {
  uint64 clock = 1;
  string installation_id = 2;
  string device_type = 3;
  string name = 4;
}

Payload

Field Name Type Description
1 clock uint64 clock value of the chat
2 installation_id string A randomly generated id that identifies this device
3 device_type string The OS of the device ios,android or desktop
4 name string The self-assigned name of the device

MembershipUpdateMessage and MembershipUpdateEvent

MembershipUpdateEvent is a message used to propagate information about group membership changes in a group chat. The details are in the Group chats specs.

Upgradability

There are two ways to upgrade the protocol without breaking compatibility:

  • A node always supports accretion
  • A node does not support deletion of existing fields or messages, which might break compatibility

Security Considerations

Changelog

Version 0.4

Released July 16, 2020

  • Added support for images
  • Added support for audio

Version 0.3

Released May 22, 2020

  • Added language to include Waku in all relevant places

Copyright

Copyright and related rights waived via CC0.